Door Monitoring Units

The DM3 is a self contained door monitoring unit requiring only an external low voltage power supply and a set of normally closed door contacts. The unit is microprocessor controlled and includes several modes of operation and programmable time options to allow the configuration of the unit to meet a variety of applications. The unit incorporates the following features:-

Internal sounder – Can be programmed to chime when the door opens, Bleep during door open and generate an alarm sound during an alarm condition.

Internal dry contact relay – With common, normally open and normally closed connections. This output can be used to activate a door open LED on Videx telephone handsets or activate external sounders and strobes.

Override key switch – The two position key switch is located on the outside of the plastic housing and can be used to disable the unit when required. For example if the door needs to be held open without the alarm going off.

Alarm trigger input – This input will set the door monitoring unit into alarm condition immediately after being triggered and will not switch off until timeout (Programmable timeout). It can be triggered using a switched negative.

Enable input – Used to monitor if a door has been opened correctly or has been forced. This 12V positive input can be taken from the unit used to release the door (i.e. Code lock, proximity reader, intercom system) and can be used to identify if a door release was authorized (i.e. the door was released by an intercom system, codelock etc).


  • Boxed low voltage door monitoring unit
  • Monitors door state using a set of door contacts
  • Internal sounder can be programmed to chime when door opens or generate alarm sound during alarm conditions
  • Override key switch to disable unit
  • Door forced alarm state
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  • Boxed – White ABS plastic
  • Dimensions – 110mm x 70mm, 30mm
  • Input voltage – 12Vdc
  • Door contact inputs – Normally closed
  • Output – Dry contact relay C, NO, NC 24Vac/dc @2A, Internal sounder
  • Input – Switched 12V override
  • Alarm input – Switched 0V
  • Door chime – Yes
  • DM3 – Door monitoring unit